Effects of a femtosecond microlens edge ladder design on visual acuity outcomes

Objective To analyze the effect of a "no trim" design in the optical ablation zone on postoperative visual quality in patients who have undergonc femtosecond microlens rescction surgery,especially with dilated pupils.Methods This was a prospective cohort study.Postoperative visual quality was measured in 3 groups of patients (a total of 104 cases,208 eyes) that included a thin flap LASIK group (38 patients,76 eyes),a femtosecond LASIK group (28 patients,56 eyes) and a femtosecond laser surgery small incision lens (SMILE) group (38 patients,76 eyes).Excimer laser cutting equipment was used in the thin flap LASIK group,optical zoom was 6.0 mm,transition zone was 1.25 mm; femtosecond laser was used for the corneal flap in the femtosecond LASIK group,optical zoom was 6.0 mm,transition zone was 1.25 mm; and femtosecond laser was used in the SMILE group for refractive microlens (6.0 mm) fabrication.Postoperative assessments included uncorrected visual acuity,contrast sensitivity (CS),glare sensitivity (GS) and wavefront aberration measurements for normal (≤5 mm) and dilated (≥7 mm) pupils.SPSS 15.0 statistical software was used for statistical analysis.Distribution normality was tested (-x±s),and then one-way ANOVA was used for overall analysis.After multiple group comparisons,differences between groups were tested with pairwise t-test comparisons.Test results were considered statistically significant at P＜0.05.Results No serious intraoperative or postoperative complications were found in the three groups.Postoperative vision with a dilated pupil reached or was higher than preoperative best corrected visual acuity.With normal pupils (5 mm or less),no statistically significant differences were found in visual contrast sensitivity among the three groups with or without glare stimulation.Also with dilated pupils (7 mm or larger),no statistically significant differences were found with or without glare.There were no statistically significant differences among the three groups for waveform spherical aberration C12 under normal pupil conditions.Whereas with dilated pupils,there were no statistically significant differences between the thin fcmtosecond LASIK and flap LASIK groups.But there were significant differences when the SMILE group was compared with the thin flap LASIK group and femtosecond LASIK group (t=2.942,P＜0.01; t=3.264,P＜0.01).The C12 values of the SMILE group (0.422±0.123) were smaller than the thin flap LASIK group (0.577±0.147) and femtosecond LASIK group (0.606-±0.158) under both pupil conditions.Conclusion Compared with “trim” thin flap LASIK and femtosecond LASIK that involved a transition region,full femtosecond microlens removal without an optical ablation zone trim design had no obvious effect on postoperative visual quality. Key words: Small incision microlensing excision ;  Femtosecond laser;  Keratomileusis,laser in situ;  Optical transition zone;  Contrast sensitivity;  Aberration